How Abiotic Petroleum Systems Work: Tectonically Driven Deep Fluid Sources

Alexander A. Kitchka
CASRE NASU, Kiev, Ukraine

Origination, maturation, migration and accumulation of abiotic hydrocarbons are immanently linked to basin dynamics and in such a way to crustal evolution and tectonic differentiation of a basin roots through geological time. A new theoretical concept for abiotic origin of petroleum attributes world's petroleum reserves to subcrust evolution of volatile-saturated zones (VSZ) characterized by high-density population of juvenile fluid inclusions enriched with hydrocarbons.
Atrophication of rifting leads to transformation of the VSZ into a transition zone at crustal-mantle interface with a regional halo of residual fluid inclusions captured during the latest riftogenic pulses. These post-rift residual fluid halos represent near-vertical domains of high fluid concentrations traced upward along primary and secondary fault zones. The next important stage of VSZ development is corresponded to “primary” petroleum migration, a process similar by analogy with that supposed for sedimentary rocks. Progressive decreasing rock elasticity in the residual post-rift crustal-mantle mixture caused by downwarping of a sedimentary basin floor and secondary overheating of fluid inclusions stimulate three-dimensional re-fracturing under augmentation of lithostatic loading and propagation of micro-cracks swarms that supply the coalescing fault zones with new flow surges of juvenile fluids. Subsidence rates are a very important parameter governing the mobilization ratio for juvenile fluids. These fluids are periodically accumulated and separated in quasi-stable fractured chambers emerging at the transition interface from unstable frictional faulting to localized quasi-plastic shearing. Ascending dilational “clouds” diverging from the aforementioned chambers along fault surfaces feed with hydrocarbons temporary traps in the crystalline basement and sedimentary cover. Typically, the temporal traps in the upper crust are associated with active or passive multilevel detachment surfaces enabling lateral migration of juvenile hydrocarbons along suprahydrostatic-circulating fluid systems.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece